STAT3 Target Research Articles

Abstract B16: STAT3 promotes ovarian cancer spheroid growth and metastasis

Abstract High-grade serous ovarian cancer remains deadly for the majority of woman who are diagnosed every year. The high mortality rate necessitates new treatment options for physicians and patients to consider. To produce new therapies, different signaling pathways that are activated in ovarian cancer need to be identified. In order to mimic the growth of ovarian cancer in the body, 3D culturing systems were used to grow clusters of ovarian cells (spheroids). Comparing gene expression from cells grown in 2D and 3D, we identified the STAT3 signaling pathway as being highly enriched in ovarian spheroids. STAT3 is a transcription factor that is activated by tyrosine phosphorylation. Once phosphorylated, STAT3 dimerizes, translocates to the nucleus, and regulates the expression of many genes involved in cell survival and migration. To determine if STAT3 was activated in 3D growing cells, we analyzed protein from cells grown in 2D and 3D and determined that STAT3 was tyrosine phosphorylated in cells grown in 3D We have found that the increase in STAT3 phosphorylation in 3D grown cells was associated with increased expression of STAT3 target genes. Consistent with this, we found enhanced STAT3 DNA binding to regulatory regions of STAT3 target genes. Recognizing that STAT3 activation is upregulated in 3D, we wanted to know if STAT3 is necessary for growth in 3D. By using siRNA to reduce the expression of STAT3, we were able to hinder the ability for ovarian cancer to grow in 3D. Moreover, reducing the expression of various components in the STAT3 signaling pathway also reduced the growth of ovarian spheroids. One of the major steps in ovarian cancer metastasis is the clearance of mesothelial cells by the cancer cells. To assess the effects of enhanced STAT3 activity in spheroids, we performed a mesothelial clearance assay with spheroids containing and lacking STAT3 expression. We found that ovarian spheroids with reduced STAT3 expression had a decreased ability to metastasize. This suggests that the STAT3 signaling pathway is a critical pathway involved in the growth and metastasis of ovarian cancer spheroids. This raises the possibility of using STAT3 inhibitors by themselves or in conjunction with standard-of-care therapeutics in the treatment of advanced ovarian cancer. Thus, targeting signaling pathways important in 3D growth may be beneficial for the treatment of ovarian cancer. Citation Format: David F. Walker, Sarah J. Lacroix, Zachary T. Giaccone, David A. Frank, Sarah R. Walker. STAT3 promotes ovarian cancer spheroid growth and metastasis [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research; 2019 Sep 13-16, 2019; Atlanta, GA. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(13_Suppl):Abstract nr B16.

TRIM14 Is a Key Regulator of the Type I IFN Response during Mycobacterium tuberculosis Infection.

Tripartite motif-containing proteins (TRIMs) play a variety of recently described roles in innate immunity. Although many TRIMs regulate type I IFN expression following cytosolic nucleic acid sensing of viruses, their contribution to innate immune signaling and gene expression during bacterial infection remains largely unknown. Because Mycobacterium tuberculosis is an activator of cGAS-dependent cytosolic DNA sensing, we set out to investigate a role for TRIM proteins in regulating macrophage responses to M. tuberculosis In this study, we demonstrate that TRIM14, a noncanonical TRIM that lacks an E3 ubiquitin ligase RING domain, is a critical negative regulator of the type I IFN response in Mus musculus macrophages. We show that TRIM14 interacts with both cGAS and TBK1 and that macrophages lacking TRIM14 dramatically hyperinduce IFN stimulated gene (ISG) expression following M. tuberculosis infection, cytosolic nucleic acid transfection, and IFN-β treatment. Consistent with a defect in resolution of the type I IFN response, Trim14 knockout macrophages have more phospho-Ser754 STAT3 relative to phospho-Ser727 and fail to upregulate the STAT3 target Socs3, which is required to turn off IFNAR signaling. These data support a model whereby TRIM14 acts as a scaffold between TBK1 and STAT3 to promote phosphorylation of STAT3 at Ser727 and resolve ISG expression. Remarkably, Trim14 knockout macrophages hyperinduce expression of antimicrobial genes like Nos2 and are significantly better than control cells at limiting M. tuberculosis replication. Collectively, these data reveal an unappreciated role for TRIM14 in resolving type I IFN responses and controlling M. tuberculosis infection.

A Brief Review on Dual Target of PARP1 and STAT3 for Cancer Therapy: A Novel Perception

Background:Cancer is a disease characterized by the uncontrolled growth and spread of abnormal cells. Around the world, over 10 million cancer cases occur annually. Half of all men and one-third of all women will develop some form of cancer during their lifetime. It is one of the most feared diseases, primarily because half of those diagnosed with cancer die from it. There are several treatments available for cancer. Almost all traditional cytotoxic agents suffer from severe toxicities and other undesirable side effects.Objective:In recent years, the development of targeted medicines has made significant achievements. Unfortunately, though these agents can block key regulators of signaling pathways in cancer, multiple compensatory pathways always attenuate pharmacological effect of single-target drugs. In addition, poor response rates and acquired drug resistance also represent a significant barrier to widespread use of targeted medicines. More recently, a number of combinatorial therapies have expanded treatment options, which can directly block several key signaling pathways and create a synergistic effect.Conclusion:Therefore, in order to overcome these barriers, the present investigation aims to develop a new strategy for designing a single molecule with inhibition of two receptors (PARP1 and STAT3) simultaneously and producing enhanced anti-cancer activity with less and/or null toxicity.

HNG, A Humanin Analogue, Promotes Hair Growth by Inhibiting Anagen-to-Catagen Transition.

The hair follicle goes through repetitive cycles including anagen, catagen, and telogen. The interaction of dermal papilla cells (DPCs) and keratinocytes regulates the hair cycle and hair growth. Humanin was discovered in the surviving brain cells of patients with Alzheimer’s disease. HNG, a humanin analogue, activates cell growth, proliferation, and cell cycle progression, and it protects cells from apoptosis. This study was performed to investigate the promoting effect and action mechanisms of HNG on hair growth. HNG significantly increased DPC proliferation. HNG significantly increased hair shaft elongation in vibrissa hair follicle organ culture. In vivo experiment showed that HNG prolonged anagen duration and inhibited hair follicle cell apoptosis, indicating that HNG inhibited the transition from the anagen to catagen phase mice. Furthermore, HNG activated extracellular signal-regulated kinase (Erk)1/2, Akt, and signal transducer and activator of transcription (Stat3) within minutes and up-regulated vascular endothelial growth factor (VEGF) levels on DPCs. This means that HNG could induce the anagen phase longer by up-regulating VEGF, which is a Stat3 target gene and one of the anagen maintenance factors. HNG stimulated the anagen phase longer with VEGF up-regulation, and it prevented apoptosis by activating Erk1/2, Akt, and Stat3 signaling.

Dietary fiber metabolites regulate innate lymphoid cell responses.

SummaryInnate lymphoid cells (ILCs) rapidly undergo expansion in population size and functional maturation in response to cytokines that signal infection, tissue damage or changes in physiology. Optimal ILC responses are shaped, in part, by the microbiota but the mechanisms remain unclear. We report that short-chain fatty acids (SCFAs), produced by the commensal microbiota from dietary fibers, support optimal expansion of ILCs, including ILC1, ILC2 and ILC3 in the intestines through their G-protein-coupled receptors (GPCRs). While this function is primarily important for intestinal ILC populations, it can also boost ILC responses in other tissues depending on host condition. ILCs express multiple GPCRs that detect SCFAs. Interestingly, we found that the expression of SCFA receptors, such as Ffar2 and Ffar3, by ILCs is induced by SCFAs. GPCR triggering by SCFAs co-stimulates the activation of Phosphoinositide 3-kinase (PI3K), Stat3, Stat5, and mammalian target of rapamycin (mTOR), which is important for ILC proliferation. While Ffar2 signaling promotes ILC2 proliferation, SCFAs can suppress ILC2 proliferation through a non-Ffar2-mediated mechanism. In conclusion, our findings indicate that SCFAs, as the major mediator of healthy microbiota and nutritional status, function to maintain optimal numbers of ILCs in peripheral tissues during infection and inflammatory responses.

THU0081 MIR-17-5P REDUCES INFLAMMATION AND BONE EROSIONS IN COLLAGEN INDUCED ARTHRITIS MICE AND DIRECTLY TARGETS THE JAK-STAT PATHWAY IN RHEUMATOID ARTHRITIS FIBROBLAST-LIKE SYNOVIOCYTES.

Background:micro-RNAs (miR) are strong regulators of gene expression. Their involvement in RA key cytokines pathway regulation entitles them as important players in RA pathophysiology. The miR 17-92 cluster has been widely studied in cancer as they regulate cell apoptosis.Objectives:The aims of this study were to screen miR 17-92 cluster’s expression in different RA phenotypes (erosive and non erosive), further elucidate the mechanisms and direct targets involved in miR-17-5p anti-inflammatory role and to investigate miR-17-5p therapeutic effect in arthritis.Methods:A miR array was performed in synovial tissue from naïve erosive and non-erosive RA patients. Intra-articular delivery of miR-17 lipoplex was performed in collagen induced arthritis model in mice. Clinical, histological and structural effects were studied over the course of arthritis. In depth studies of miR-17 mechanisms of action were performed in primary RA-FLS isolated from RA synovial tissue.Results:Among others, miR-17-5p expression was reduced in erosive RA. miR-17 transfection in arthritic paws significantly reduced clinical inflammation. Moreover, synovial B cells, T cells, macrophages and polynuclear neutrophils infiltrates were significantly reduced. Structural damage was also decreased as shown by a reduction in the number of osteoclasts and erosion score by CT analysis. Pro-inflammatory cytokines of the IL-6 family, STAT3 target genes and IL-1β expression were also significantly reduced, but not TNF-alpha. miR17 directly targeted the 3’-untranslated region of STAT3 and JAK1. STAT3 and JAK1 mRNA and protein expression were reduced in RA-FLS following miR-17 transfection. STAT3 and JAK1 mRNA and activation of STAT3 as assessed by immunohistochemistry were also reduced in injected paws.Conclusion:We demonstrate an anti-inflammatory and anti-erosive role of miR-17 in vivo. This effect involves the suppression of the IL-6 family autocrine amplifying loop through the direct targeting of JAK1 and STAT3 as shown in RA-FLS.FigureEffect of miR-17 lipoplex injection in Collagen induced arthritis (CIA) mice’s ankles.Disclosure of Interests:None declared

Targeting STAT3 signaling using stabilised sulforaphane (SFX-01) inhibits endocrine resistant stem-like cells in ER-positive breast cancer

Estrogen receptor (ER) positive breast cancer is frequently sensitive to endocrine therapy. Multiple mechanisms of endocrine therapy resistance have been identified, including cancer stem-like cell (CSC) activity. Here we investigate SFX-01, a stabilised formulation of sulforaphane (SFN), for its effects on breast CSC activity in ER+ preclinical models. SFX‐01 reduced mammosphere formation efficiency (MFE) of ER+ primary and metastatic patient samples. Both tamoxifen and fulvestrant increased MFE and aldehyde dehydrogenase (ALDH) activity of patient-derived xenograft (PDX) tumors, which was reversed by combination with SFX‐01. SFX-01 significantly reduced tumor-initiating cell frequency in secondary transplants and reduced the formation of spontaneous lung micrometastases by PDX tumors in mice. Mechanistically, we establish that both tamoxifen and fulvestrant induce STAT3 phosphorylation. SFX-01 suppressed phospho‐STAT3 and SFN directly bound STAT3 in patient and PDX samples. Analysis of ALDH+ cells from endocrine-resistant patient samples revealed activation of STAT3 target genes MUC1 and OSMR, which were inhibited by SFX-01 in patient samples. Increased expression of these genes after 3 months’ endocrine treatment of ER+ patients (n = 68) predicted poor prognosis. Our data establish the importance of STAT3 signaling in CSC-mediated resistance to endocrine therapy and the potential of SFX-01 for improving clinical outcomes in ER+ breast cancer.

Luteolin and Apigenin Attenuate LPS-Induced Astrocyte Activation and Cytokine Production by Targeting MAPK, STAT3, and NF-κB Signaling Pathways.

Astrocytes release biologically active substances that cause inflammation in neurodegenerative diseases. The present study investigated the effects of two flavonoids (apigenin and luteolin) on the production of IL-31 and IL-33 in lipopolysaccharide (LPS)-activated astrocytes. Cell viability was investigated using EZ-Cytox assay, mRNA expressions of IL-31 and IL-33 were analyzed by RT-PCR, protein expressions were analyzed by western blot, and cytokine secretion was analyzed by ELISA. Apigenin and luteolin prevented astrocyte activation and inhibited mRNA and protein expression and secretion of IL-31 and IL-33 in the LPS-treated astrocytes. Apigenin's suppression of ERK, NF-κB, and STAT3 activations was responsible for the inhibition of IL-31 and IL-33, while luteolin's suppression of JNK, p38, ERK, NF-κB, and STAT3 activations was responsible for the inhibition of IL-31 in the astrocytes. Also, luteolin's suppression of ERK, NF-κB, and STAT3 activations inhibited IL-33 production in the activated astrocytes. In addition, apigenin and luteolin also prevented the translocation of activated STAT3 and NF-κB to the nucleus of the activated astrocytes and subsequently affected their DNA binding activities. The results suggest that apigenin and luteolin may have potentials as neuroprotective agents for the treatment of diseases involving astrocyte activation and detrimental production of IL-31 and IL-33.

The biomarker HE4 (WFDC2) promotes a pro-angiogenic and immunosuppressive tumor microenvironment via regulation of STAT3 target genes

Epithelial ovarian cancer (EOC) is a highly lethal gynecologic malignancy arising from the fallopian tubes that has a high rate of chemoresistant recurrence and low five-year survival rate. The ovarian cancer biomarker HE4 is known to promote proliferation, metastasis, chemoresistance, and suppression of cytotoxic lymphocytes. In this study, we sought to examine the effects of HE4 on signaling within diverse cell types that compose the tumor microenvironment. HE4 was found to activate STAT3 signaling and promote upregulation of the pro-angiogenic STAT3 target genes IL8 and HIF1A in immune cells, ovarian cancer cells, and endothelial cells. Moreover, HE4 promoted increases in tube formation in an in vitro model of angiogenesis, which was also dependent upon STAT3 signaling. Clinically, HE4 and IL8 levels positively correlated in ovarian cancer patient tissue. Furthermore, HE4 serum levels correlated with microvascular density in EOC tissue and inversely correlated with cytotoxic T cell infiltration, suggesting that HE4 may cause deregulated blood vessel formation and suppress proper T cell trafficking in tumors. Collectively, this study shows for the first time that HE4 has the ability to affect signaling events and gene expression in multiple cell types of the tumor microenvironment, which could contribute to angiogenesis and altered immunogenic responses in ovarian cancer.

Impact of Epstein-Barr Virus LMP2A-dependent BTK/STAT3 activation on resting and activated murine B cells

Abstract Epstein-Barr virus (EBV) latently infects over 90% of the population and is associated with the development of numerous autoimmune diseases and B cell lymphomas. Therefore, understanding the impact of latency proteins on B cell survival and function is vital. One EBV latency protein, LMP2A, acts as a BCR mimic to promote B cell survival, increase B cell activation, and accelerate tumor development in murine mouse models. Our laboratory identified that LMP2A activates the PI3K/BTK/STAT3 pathway in human B cell lymphomas to increase IL-10 production that promotes survival. However, the ability of LMP2A to activate BTK and STAT3 in non-transformed B cells is unknown. To test this possibility, we returned to the LMP2A transgenic mouse model as a source of resting B cells that express LMP2A. To determine if LMP2A activates STAT3 in the mouse model, resting B cells from wildtype and LMP2A-transgenic mice were isolated and STAT3 phosphorylation was assessed by Western blot analysis. Our data indicate that LMP2A-postitive B cells express higher levels of phosphorylated STAT3 than wildtype controls. We further analyzed whether the LMP2A-dependent activation of STAT3 resulted in an increase in STAT3-dependent targets. Flow cytometric analysis indicates that the addition of STAT3 inhibitors to activated LMP2A-expressing B cells blocked the LMP2A-dependent increase in STAT3 targets in comparison to wildtype controls. These data suggest that LMP2A increases the activation of the oncogene STAT3 in resting B cells, which may contribute to the development of EBV-associated tumors and autoimmune diseases.

STAT3 modulates metabolic programming of inflammation-induced macrophages

Abstract Redox homeostasis in an inflammatory environment is crucial to ensure a balanced immune response. Several inflammatory disorders are associated with impairment of redox homeostasis, leading to DNA damage and subsequent immune dysregulation. The transcription factor STAT3 has anti-inflammatory activity in myeloid cells, mediated by inhibition of Ubc13, a key Toll-like receptor (TLR) signaling component. STAT3 anti-inflammatory activity is crucial in protection from systemic inflammation, maintenance of lineage-balanced hematopoiesis, and inhibition of DNA damage accumulation in hematopoietic progenitors. The molecular cues by which STAT3 mitigates DNA damage in an inflammatory environment, however, are poorly understood. Recently, we found that STAT3-deficient bone marrow derived-macrophages (BMDMs) exhibited increased oxidative stress upon TLR4 stimulation, including reduced antioxidant amounts and elevated production of reactive oxygen species (ROS). These responses were accompanied by increased gH2AX foci formation, suggesting accumulation of DNA damage. By contrast, BMDMs lacking Ubc13 exhibited increased expression of antioxidants and reduced DNA damage. RNA-sequencing analysis identified transcriptional targets of STAT3 and Ubc13 in steady state and TLR-stimulated BMDMs. Collectively, our findings suggest STAT3-mediated control of Ubc13 is important in regulating inflammation-induced oxidative stress and DNA damage by modulating antioxidant signaling and DNA damage repair pathways. Thus, STAT3 plays a crucial role in metabolic reprogramming of macrophages during inflammation to preserve redox homeostasis.

Leukemia Inhibitory Factor Inhibits Plasmacytoid Dendritic Cell Function and Development.

Plasmacytoid dendritic cells (pDCs) produce abundant type I IFNs (IFN-I) in response to viral nucleic acids. Generation of pDCs from bone marrow dendritic cell (DC) progenitors and their maintenance is driven by the transcription factor E2-2 and inhibited by its repressor Id2. In this study, we find that mouse pDCs selectively express the receptor for LIF that signals through STAT3. Stimulation of pDCs with LIF inhibited IFN-I, TNF, and IL-6 responses to CpG and induced expression of the STAT3 targets SOCS3 and Bcl3, which inhibit IFN-I and NF-κB signaling. Moreover, although STAT3 has been also reported to induce E2-2, LIF paradoxically induced its repressor Id2. A late-stage bone marrow DC progenitor expressed low amounts of LIFR and developed into pDCs less efficiently after being exposed to LIF, consistent with the induction of Id2. Conversely, pDC development and serum IFN-I responses to lymphocytic choriomeningitis virus infection were augmented in newly generated mice lacking LIFR in either CD11c+ or hematopoietic cells. Thus, an LIF-driven STAT3 pathway induces SOCS3, Bcl3, and Id2, which render pDCs and late DC progenitors refractory to physiological stimuli controlling pDC functions and development. This pathway can be potentially exploited to prevent inappropriate secretion of IFN-I in autoimmune diseases or promote IFN-I secretion during viral infections.

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Intervention mechanism of Qingwen Baidu Yin on cytokine storm based on network pharmacology

The aim of this paper was to explore the intervention mechanism of Qingwen Baidu Yin in cytokine storm based on network pharmacology. TCMSP and TCMIP V2.0 server were used to predict all chemical components and action targets of Qingwen Baidu Yin. Diseases that could be treated by Qingwen Baidu Yin were predicted through Enrichr database. A compound target interaction(PPI) network diagram was constructed using STRING 11.0. OmicShare was used to analyzed the gene ontology(GO) enrichment and enrichment of the Kyoto encyclopedia of genes and genomes(KEGG) pathway of core targets. Component-target-path network diagram was constructed with Cytoscape 3.6.0 software. After analysis of the database, 267 compounds were screened for Qingwen Baidu Yin, involving 1 450 targets, and a protein interaction network was constructed. Total 219 core target proteins were predicted, such as NFKB1, STAT1, RAF1, IL2, JAK1, IL6, TNF, BCL2 and other important targets, and 221 core target pathways were enriched, including cancer pathway, Kaposi's sarcoma-associated herpes virus infection, chemokine signal pathway, PI3 K-AKT signal pathway, EB virus infection, virus carcinogenesis and T cell receptor signaling pathways, a collection of which were highly related to cytokine storms. GO annotation analysis suggested that Qingwen Baidu Yin Decoction may exert therapeutic effects by regulating protein phosphorylation, cell response to cytokine stimulation, cell proliferation, inflammatory response, transmembrane receptor protein tyrosine kinase signaling pathway, and cytokine-mediated signaling pathways. This study revealed potential active components of Qingwen Baidu Yin in defending against cytokine storm and its possible mechanism of action, and provided theoretical basis and technical support for further clinical application of this prescription.

Combined Src/EGFR Inhibition Targets STAT3 Signaling and Induces Stromal Remodeling to Improve Survival in Pancreatic Cancer.

Lack of durable response to cytotoxic chemotherapy is a major contributor to the dismal outcomes seen in pancreatic ductal adenocarcinoma (PDAC). Extensive tumor desmoplasia and poor vascular supply are two predominant characteristics which hinder the delivery of chemotherapeutic drugs into PDAC tumors and mediate resistance to therapy. Previously, we have shown that STAT3 is a key biomarker of therapeutic resistance to gemcitabine treatment in PDAC, which can be overcome by combined inhibition of the Src and EGFR pathways. Although it is well-established that concurrent EGFR and Src inhibition exert these antineoplastic properties through direct inhibition of mitogenic pathways in tumor cells, the influence of this combined therapy on stromal constituents in PDAC tumors remains unknown. In this study, we demonstrate in both orthotopic tumor xenograft and Ptf1acre/+;LSL-KrasG12D/+;Tgfbr2flox/flox (PKT) mouse models that concurrent EGFR and Src inhibition abrogates STAT3 activation, increases microvessel density, and prevents tissue fibrosis in vivo. Furthermore, the stromal changes induced by parallel EGFR and Src pathway inhibition resulted in improved overall survival in PKT mice when combined with gemcitabine. As a phase I clinical trial utilizing concurrent EGFR and Src inhibition with gemcitabine has recently concluded, these data provide timely translational insight into the novel mechanism of action of this regimen and expand our understanding into the phenomenon of stromal-mediated therapeutic resistance. IMPLICATIONS: These findings demonstrate that Src/EGFR inhibition targets STAT3, remodels the tumor stroma, and results in enhanced delivery of gemcitabine to improve overall survival in a mouse model of PDAC.

Chronic Regulation of miR-124-3p in the Perilesional Cortex after Experimental and Human TBI.

Traumatic brain injury (TBI) dysregulates microRNAs, which are the master regulators of gene expression. Here we investigated the changes in a brain-enriched miR-124-3p, which is known to associate with major post-injury pathologies, such as neuroinflammation. RT-qPCR of the rat tissue sampled at 7 d and 3 months in the perilesional cortex adjacent to the necrotic lesion core (aPeCx) revealed downregulation of miR-124-3p at 7 d (fold-change (FC) 0.13, p < 0.05 compared with control) and 3 months (FC 0.40, p < 0.05) post-TBI. In situ hybridization confirmed the downregulation of miR-124-3p at 7 d and 3 months post-TBI in the aPeCx (both p < 0.01). RT-qPCR confirmed the upregulation of the miR-124-3p target Stat3 in the aPeCx at 7 d post-TBI (7-fold, p < 0.05). mRNA-Seq revealed 312 downregulated and 311 upregulated miR-124 targets (p < 0.05). To investigate whether experimental findings translated to humans, we performed in situ hybridization of miR-124-3p in temporal lobe autopsy samples of TBI patients. Our data revealed downregulation of miR-124-3p in individual neurons of cortical layer III. These findings indicate a persistent downregulation of miR-124-3p in the perilesional cortex that might contribute to post-injury neurodegeneration and inflammation.

Ethacrynic acid inhibits STAT3 activity through the modulation of SHP2 and PTP1B tyrosine phosphatases in DU145 prostate carcinoma cells

To identify signal transducer and activator of transcription factor 3 (STAT3) inhibitors, we generated STAT3-dependent gene expression signature by analyzing gene expression profiles of DU145 cancer cells treated with STAT3 inhibitor, piperlongumine and 2-hydroxycinnamaldehyde. Then we explored gene expression signature-based strategies using a connectivity map database and identified several STAT3 inhibitors, including ethacrynic acid (EA). EA is currently used as a diuretic drug. EA inhibited STAT3 activation in DU145 prostate cancer cells and consequently decreased the levels of STAT3 target genes such as cyclin A and MCL-1. Furthermore, EA treatment inhibited tumor growth in mice xenografted with DU145 cells and decreased p-STAT3 expression in tumor tissues. Knockdown of Src homology region 2 domain-containing phosphatase-2 (SHP2) or Protein tyrosine phosphatase 1B (PTP1B) gene expression by siRNA suppressed the ability of EA to inhibit STAT3 activation. When EA was combined with an activator of SHP2 or PTP1B, p-STAT3 expression was synergistically decreased; when EA was combined with an inhibitor of SHP2 or PTP1B, p-STAT3 expression was rescued. By using an affinity pulldown assay with biotinyl-EA, EA was shown to associate with SHP2 and PTP1B in vitro. Additionally, the drug affinity responsive target stability (DARTS) assay confirmed the direct binding of EA to SHP2 and PTP1B. SHP2 is activated by EA through active phosphorylation at Y580 and direct binding to SHP2. Collectively, our results suggest that EA inhibits STAT3 activity through the modulation of phosphatases such as SHP2 and PTP1B and may be a potential anticancer drug to target STAT3 in cancer progression.

Janus kinase 2 inhibition by Licochalcone B suppresses esophageal squamous cell carcinoma growth.

Esophageal cancer (EC) is one of the leading causes to cancer death in the worldwide and major population of EC is esophageal squamous cell carcinoma (ESCC). Still, ESCC-targeted therapy has not been covered yet. In the present study we have identified that Licochalcone B (Lico B) inhibited the ESCC growth by directly blocking the Janus kinase (JAK) 2 activity and its downstream signaling pathway. Lico B suppressed KYSE450 and KYSE510 ESCC cell growth, arrested cell cycle at G2/M phase and induced apoptosis. Direct target of Lico B was identified by kinase assay and verified with in vitro and ex vivo binding. Computational docking model predicted for Lico B interaction to ATP-binding pocket of JAK2. Furthermore, treatment of JAK2 clinical medicine AZD1480 to ESCC cells showed similar tendency with Lico B. Thus, JAK2 downstream signaling proteins phosphorylation of STAT3 at Y705 and S727 as well as STAT3 target protein Mcl-1 expression was decreased with treatment of Lico B. Our results suggest that Lico B inhibits ESCC cell growth, arrests cell cycle and induces apoptosis, revealing the underlying mechanism involved in JAK2/STAT3 signaling pathways after Lico B treatment. It might provide potential role of Lico B in the treatment of ESCC.

Signaling mechanisms of growth hormone-releasing hormone receptor in LPS-induced acute ocular inflammation

Ocular inflammation is a major cause of visual impairment attributed to dysregulation of the immune system. Previously, we have shown that the receptor for growth-hormone-releasing hormone (GHRH-R) affects multiple inflammatory processes. To clarify the pathological roles of GHRH-R in acute ocular inflammation, we investigated the inflammatory cascades mediated by this receptor. In human ciliary epithelial cells, the NF-κB subunit p65 was phosphorylated in response to stimulation with lipopolysaccharide (LPS), resulting in transcriptional up-regulation of GHRH-R. Bioinformatics analysis and coimmunoprecipitation showed that GHRH-R had a direct interaction with JAK2. JAK2, but not JAK1, JAK3, and TYK2, was elevated in ciliary body and iris after treatment with LPS in a rat model of endotoxin-induced uveitis. This elevation augmented the phosphorylation of STAT3 and production of proinflammatory factors, including IL-6, IL-17A, COX2, and iNOS. In explants of iris and ciliary body, the GHRH-R antagonist, MIA-602, suppressed phosphorylation of STAT3 and attenuated expression of downstream proinflammatory factors after LPS treatment. A similar suppression of STAT3 phosphorylation was observed in human ciliary epithelial cells. In vivo studies showed that blocking of the GHRH-R/JAK2/STAT3 axis with the JAK inhibitor Ruxolitinib alleviated partially the LPS-induced acute ocular inflammation by reducing inflammatory cells and protein leakage in the aqueous humor and by repressing expression of STAT3 target genes in rat ciliary body and iris and in human ciliary epithelial cells. Our findings indicate a functional role of the GHRH-R/JAK2/STAT3-signaling axis in acute anterior uveitis and suggest a therapeutic strategy based on treatment with antagonists targeting this signaling pathway.

Celastrol Attenuates Angiotensin II-Induced Cardiac Remodeling by Targeting STAT3.

Excessive Ang II (angiotensin II) levels lead to a profibrotic and hypertrophic milieu that produces deleterious remodeling and dysfunction in hypertension-associated heart failure. Agents that disrupt Ang II-induced cardiac dysfunction may have clinical utility in the treatment of hypertension-associated heart failure. We have examined the potential effect of celastrol-a bioactive compound derived from the Celastraceae family-on Ang II-induced cardiac dysfunction. In rat primary cardiomyocytes and H9C2 (rat cardiomyocyte-like H9C2) cells, celastrol attenuates Ang II-induced cellular hypertrophy and fibrotic responses. Proteome microarrays, surface plasmon resonance, competitive binding assays, and molecular simulation were used to identify the molecular target of celastrol. Our data showed that celastrol directly binds to and inhibits STAT (signal transducer and activator of transcription)-3 phosphorylation and nuclear translocation. Functional tests demonstrated that the protection of celastrol is afforded through targeting STAT3. Overexpression of STAT3 dampens the effect of celastrol by partially rescuing STAT3 activity. Finally, we investigated the in vivo effect of celastrol treatment in mice challenged with Ang II and in the transverse aortic constriction model. We show that celastrol administration protected heart function in Ang II-challenged and transverse aortic constriction-challenged mice by inhibiting cardiac fibrosis and hypertrophy. Our studies show that celastrol inhibits Ang II-induced cardiac dysfunction by inhibiting STAT3 activity.